Arizona Governor Jan Brewer made her much-anticipated endorsement in the Republican presidential nomination contest earlier today on NBC’s Meet the Press — and it went to Mitt Romney, who once had a huge lead in her state but has struggled to maintain an edge over Rick Santorum. Will Brewer’s pick help Romney lock up the winner-take-all state on Tuesday?

Brewer, in Washington, D.C. for the National Governors Association Winter Meeting, said Romney had “carried the day” and that she was going to work on his behalf.

“I have had my debate there in Arizona, and I have looked over all the wonderful people that have put themselves up for nomination, and I have decided that I am going to publicly endorse Mitt Romney,” Brewer said. “I think he’s the man that carried the day, and I am going to get out there and work as hard as I know how to make sure that he wins Arizona and work in other places of our country to see that he wins those places, too.”

Brewer cited his business prowess and past political history as her reasons for the endorsement.

“I think that he handles himself very, very well, but more than that I think he has the pro-business background and he has that political history that I think that he would serve America the best of all the candidates,” she said. “So it was a difficult decision, but I think Mitt is by far the person that can go in and win.”

Gubernatorial endorsements haven’t exactly been game-changers thus far in the primaries. Nikki Haley endorsed Romney in South Carolina, only to see Newt Gingrich beat him by double digits. Rick Perry endorsed Gingrich after Perry withdrew in South Carolina, and Gingrich lost Florida by almost as much as he won South Carolina, and trails badly in Texas at the moment. In Michigan, Romney got Rick Snyder’s endorsement on February 15th, but the best that can be said about it is that it didn’t move the polling.

Arizona might be different, however. Brewer has had a stronger relationship with grassroots conservatives in her state, especially after taking on Barack Obama over immigration enforcement. She carries the kind of credibility on the Right at the moment that Romney desperately needs. Her endorsement will also reinforce the subtext of the election for Republicans that the main issues for November will be the economy and Obama himself. Brewer’s standing on a national basis will also help Romney in other states besides Arizona, which is almost certainly not the case with Snyder and Haley.

The polls have already begun a swing back to Romney after Santorum’s mediocre performance on Wednesday, and this may help Romney build momentum in the final two days before Tuesday’s primaries in Arizona and Michigan. If he wins both, Santorum’s hopes for a Super Tuesday surprise will begin to dim. And don’t be surprised if people start talking about a Romney-Brewer ticket if that comes to pass.

Update: A commenter corrects me, rightly, that Perry endorsed Gingrich after his own withdrawal in South Carolina but before the primary. I’ve edited that passage for greater accuracy.